Question: An ideal diesel engine has a compression

> Why is excessive moisture in steam undesirable in steam turbines? What is the highest moisture content allowed?

> Why is the Carnot cycle not a realistic model for steam power plants?

> Repeat Prob. 9–90 for a regenerator effectiveness of 70 percent. Data from Prob. 9-90: Air enters the compressor of a regenerative gas-turbine engine at 310 K and 100 kPa, where it is compressed to 900 kPa and 650 K. The regenerator has an effectiveness

> Repeat Prob. 9–90 using constant specific heats at room temperature. Data from Prob. 9-90: Air enters the compressor of a regenerative gas-turbine engine at 310 K and 100 kPa, where it is compressed to 900 kPa and 650 K. The regenerator has an effective

> Air enters the compressor of a regenerative gas-turbine engine at 310 K and 100 kPa, where it is compressed to 900 kPa and 650 K. The regenerator has an effectiveness of 80 percent, and the air enters the turbine at 1400 K. For a turbine efficiency of 90

> What is the difference between spark-ignition and compression-ignition engines?

> A stationary gas-turbine power plant operates on an ideal regenerative Brayton cycle (∊ = 100 percent) with air as the working fluid. Air enters the compressor at 95 kPa and 290 K and the turbine at 880 kPa and 1100 K. Heat is transferred to air from an

> A Brayton cycle with regeneration using air as the working fluid has a pressure ratio of 7. The minimum and maximum temperatures in the cycle are 310 and 1150 K. Assuming an isentropic efficiency of 75 percent for the compressor and 82 percent for the tu

> A gas-turbine engine operates on the ideal Brayton cycle with regeneration. Now the regenerator is rearranged so that the airstreams of states 2 and 5 enter at one end of the regenerator and streams 3 and 6 exit at the other end (i.e., parallel flow arra

> The specific weight of a system is defined as the weight per unit volume (note that this definition violates the normal specific property-naming convention). Is the specific weight an extensive or intensive property?

> Rework Prob. 9–85 when the compressor isentropic efficiency is 87 percent and the turbine isentropic efficiency is 90 percent. Data from Prob. 9-85: A gas turbine for an automobile is designed with a regenerator. Air enters the compres

> A gas turbine for an automobile is designed with a regenerator. Air enters the compressor of this engine at 100 kPa and 30°C. The compressor pressure ratio is 8; the maximum cycle temperature is 800°C; and the cold airstream leaves

> Develop an expression for the thermal efficiency of an ideal Brayton cycle with an ideal regenerator of effectiveness 100 percent. Use constant specific heats at room temperature.

> In 1903, Aegidius Elling of Norway designed and built an 11-hp gas turbine that used steam injection between the combustion chamber and the turbine to cool the combustion gases to a safe temperature for the materials available at the time. Currently ther

> In an ideal regenerator, is the air leaving the compressor heated to the temperature at (a) the turbine inlet, (b) the turbine exit, (c) slightly above the turbine exit?

> Somebody claims that at very high pressure ratios, the use of regeneration actually decreases the thermal efficiency of a gas-turbine engine. Is there any truth in this claim? Explain.

> Define the effectiveness of a regenerator used in gasturbine cycles.

> Can the mean effective pressure of an automobile engine in operation be less than the atmospheric pressure?

> How does regeneration affect the efficiency of a Brayton cycle, and how does it accomplish it?

> A gas-turbine power plant operates on a modified Brayton cycle shown in the figure with an overall pressure ratio of 8. Air enters the compressor at 0°C and 100 kPa. The maximum cycle temperature is 1500 K. The compressor and the turbines are

> What is the difference between intensive and extensive properties?

> A simple ideal Brayton cycle uses argon as the working fluid. At the beginning of the compression, P1 = 15 psia and T1 = 80°F; the maximum cycle temperature is 1200°F; and the pressure in the combustion chamber is 150 psia. The argon enters the compres

> A gas-turbine power plant operates on the simple Brayton cycle between the pressure limits of 100 and 1600 kPa. The working fluid is air, which enters the compressor at 40°C at a rate of 850 m3/min and leaves the turbine at 650°C.

> Repeat Prob. 9–74 for a pressure ratio of 15. Data from Prob. 9-74: An aircraft engine operates on a simple ideal Brayton cycle with a pressure ratio of 10. Heat is added to the cycle at a rate of 500 kW; air passes through the engine at a rate of 1 kg/

> An aircraft engine operates on a simple ideal Brayton cycle with a pressure ratio of 10. Heat is added to the cycle at a rate of 500 kW; air passes through the engine at a rate of 1 kg/s; and the air at the beginning of the compression is at 70 kPa and 0

> Air is used as the working fluid in a simple ideal Brayton cycle that has a pressure ratio of 12, a compressor inlet temperature of 300 K, and a turbine inlet temperature of 1000 K. Determine the required mass flow rate of air for a net power output of 7

> Repeat Prob. 9–69 when the isentropic efficiencies of the turbine and compressor are 90 percent and 80 percent, respectively, and there is a 50-kPa pressure drop across the combustion chamber. Data from Prob. 9-69: A simple ideal Brayt

> Repeat Prob. 9–69 when the isentropic efficiency of the turbine is 90 percent and that of the compressor is 80 percent. Data from Prob. 9-69: A simple ideal Brayton cycle operates with air with minimum and maximum temperatures of 27&Ac

> Repeat Prob. 9–69 when the isentropic efficiency of the turbine is 90 percent. Data from Prob. 9-69: A simple ideal Brayton cycle operates with air with minimum and maximum temperatures of 27°C and 727°C. It is de

> Define the compression ratio for reciprocating engines.

> A simple ideal Brayton cycle operates with air with minimum and maximum temperatures of 27°C and 727°C. It is designed so that the maximum cycle pressure is 2000 kPa and the minimum cycle pressure is 100 kPa. Determine the net work

> How would you describe the state of the air in the atmosphere? What kind of process does this air undergo from a cool morning to a warm afternoon?

> Repeat Prob. 9–67 using constant specific heats at room temperature. Data from Prob. 9-67: A gas-turbine power plant operates on the simple Brayton cycle with air as the working fluid and delivers 32 MW of power. The minimum and maximum temperatures in

> A gas-turbine power plant operates on the simple Brayton cycle with air as the working fluid and delivers 32 MW of power. The minimum and maximum temperatures in the cycle are 310 and 900 K, and the pressure of air at the compressor exit is 8 times the v

> A stationary gas-turbine power plant operates on a simple ideal Brayton cycle with air as the working fluid. The air enters the compressor at 95 kPa and 290 K and the turbine at 760 kPa and 1100 K. Heat is transferred to air at a rate of 35,000 kJ/s. Det

> A simple ideal Brayton cycle with air as the working fluid has a pressure ratio of 10. The air enters the compressor at 520 R and the turbine at 2000 R. Accounting for the variation of specific heats with temperature, determine (a) the air temperature at

> How do the inefficiencies of the turbine and the compressor affect (a) the back work ratio and (b) the thermal efficiency of a gas-turbine engine?

> Why are the back work ratios relatively high in gas-turbine engines?

> What is the back work ratio? What are typical back work ratio values for gas-turbine engines?

> For fixed maximum and minimum temperatures, what is the effect of the pressure ratio on (a) the thermal efficiency and (b) the net work output of a simple ideal Brayton cycle?

> What four processes make up the simple ideal Brayton cycle?

> What does the area enclosed by the cycle represent on a P-v diagram? How about on a T-s diagram?

> How would you define a system to determine the temperature rise created in a lake when a portion of its water is used to cool a nearby electrical power plant?

> Repeat Prob. 9–58E if the compression ratio is reduced to 12. Data from Prob. 9-58: An air-standard dual cycle has a compression ratio of 20 and a cutoff ratio of 1.3. The pressure ratio during the constant volume heat addition process is 1.2. Determine

> An air-standard dual cycle has a compression ratio of 20 and a cutoff ratio of 1.3. The pressure ratio during the constant volume heat addition process is 1.2. Determine the thermal efficiency, amount of heat added, and the maximum gas pressure and tempe

> Repeat Prob. 9–56 using nitrogen as the working fluid. Data from Prob. 9-56: A four-cylinder, two-stroke 2.4-L diesel engine that operates on an ideal Diesel cycle has a compression ratio of 22 and a cutoff ratio of 1.8. Air is at 70°C and 97 kPa at the

> A four-cylinder, two-stroke 2.4-L diesel engine that operates on an ideal Diesel cycle has a compression ratio of 22 and a cutoff ratio of 1.8. Air is at 70°C and 97 kPa at the beginning of the compression process. Using the cold-air-standard assumptions

> Reconsider Prob. 9–54. Using appropriate software, study the effect of varying the compression ratio from 14 to 24. Plot the net work output, mean effective pressure, and thermal efficiency as a function of the compression ratio. Plot the T-s and P-v dia

> Repeat Prob. 9–53, but replace the isentropic expansion process with a polytropic expansion process with the polytropic exponent n = 1.35. Use variable specific heats. Data from Prob. 9-53: An ideal diesel engine has a compression ratio of 20 and uses a

> An ideal Diesel cycle has a maximum cycle temperature of 2000°C. The state of the air at the beginning of the compression is P1 = 95 kPa and T1 = 15°C. This cycle is executed in a four-stroke, eight-cylinder engine with a cylinder bore of 10 cm and a pis

> Repeat Prob. 9–50E using constant specific heats at room temperature. Data from Prob. 9-50: An air-standard Diesel cycle has a compression ratio of 18.2. Air is at 120°F and 14.7 psia at the beginning of the compression process and at 3200 R at the end

> An air-standard Diesel cycle has a compression ratio of 18.2. Air is at 120°F and 14.7 psia at the beginning of the compression process and at 3200 R at the end of the heat-addition process. Accounting for the variation of specific heats with temperature

> A pressure gage connected to a tank reads 50 psi at a location where the barometric reading is 29.1 in Hg. Determine the absolute pressure in the tank. Take ρHg = 848.4 lbm/ft3.

> How are the combustion and exhaust processes modeled under the air-standard assumptions?

> Repeat Prob. 9–48 using constant specific heats at room temperature. Data from Prob. 9-48: An air-standard Diesel cycle has a compression ratio of 16 and a cutoff ratio of 2. At the beginning of the compression process, air is at 95 kPa and 27°C. Accoun

> An air-standard Diesel cycle has a compression ratio of 16 and a cutoff ratio of 2. At the beginning of the compression process, air is at 95 kPa and 27°C. Accounting for the variation of specific heats with temperature, determine (a) the temperature aft

> Rework Prob. 9–46 when the isentropic compression efficiency is 90 percent and the isentropic expansion efficiency is 95 percent. Data from Prob. 9-46: An ideal Diesel cycle has a compression ratio of 18 and a cutoff ratio of 1.5. Determine the maximum

> An ideal Diesel cycle has a compression ratio of 18 and a cutoff ratio of 1.5. Determine the maximum air temperature and the rate of heat addition to this cycle when it produces 200 hp of power; the cycle is repeated 1200 times per minute; and the state

> Do diesel or gasoline engines operate at higher compression ratios? Why?

> If the pressure of a substance is increased during a boiling process, will the temperature also increase or will it remain constant? Why?

> For a specified compression ratio, is a diesel or gasoline engine more efficient?

> Does water boil at higher temperatures at higher pressures? Explain.

> What is the cutoff ratio? How does it affect the thermal efficiency of a Diesel cycle?

> The maximum safe air pressure of a tire is typically written on the tire itself. The label on a tire indicates that the maximum pressure is 35 psi (gage). Express this maximum pressure in kPa.

> What is the net force acting on a car cruising at a constant velocity of 70 km/h (a) on a level road and (b) on an uphill road?

> What is vapor pressure? How is it related to saturation pressure?

> How does the ideal Diesel cycle differ from the ideal Otto cycle?

> What is a boundary layer? What causes a boundary layer to develop?

> How does a diesel engine differ from a gasoline engine?

> Even though steel is about 7 to 8 times denser than water, a steel paper clip or razor blade can be made to float on water! Explain and discuss. Predict what would happen if you mix some soap with the water.

> When we double the compression ratio of an ideal Otto cycle, what happens to the maximum gas temperature and pressure when the state of the air at the beginning of the compression and the amount of heat addition remain the same? Use constant specific hea

> A fluid between two very long parallel plates is heated in a way that its viscosity decreases linearly from 0.90 Paâ‹…s at the lower plate to 0.50 Paâ‹…s at the upper plate. The spacing between the two plates is 0.4 mm. Th

> How does the thermal efficiency of an ideal cycle, in general, compare to that of a Carnot cycle operating between the same temperature limits?

> Some rocks or bricks contain small air pockets in them and have a spongy structure. Assuming the air spaces form columns of an average diameter of 0.006 mm, determine how high water can rise in such a material. Take the surface tension of the air–water i

> Repeat Prob. 9–38E using argon as the working fluid. Data from Prob. 9-38: An ideal Otto cycle with air as the working fluid has a compression ratio of 8. The minimum and maximum temperatures in the cycle are 540 and 2400 R. Accounting for the variation

> A vacuum gage connected to a chamber reads 35 kPa at a location where the atmospheric pressure is 92 kPa. Determine the absolute pressure in the chamber.

> A 10-cm-diameter cylindrical shaft rotates inside a 50-cm-long, 10.3-cm-diameter bearing. The space between the shaft and the bearing is completely filled with oil whose viscosity at anticipated operating temperature is 0.300 N⋅s/m2. Determine the power

> An ideal Otto cycle with air as the working fluid has a compression ratio of 8. The minimum and maximum temperatures in the cycle are 540 and 2400 R. Accounting for the variation of specific heats with temperature, determine (a) the amount of heat transf

> Derive a relation for the capillary rise of a liquid between two large parallel plates a distance t apart inserted into the liquid vertically. Take the contact angle to be f.

> A six-cylinder, 4-L spark-ignition engine operating on the ideal Otto cycle takes in air at 90 kPa and 20°C. The minimum enclosed volume is 15 percent of the maximum enclosed volume. When operated at 2500 rpm, this engine produces 90 hp. Determine the ra

> The variation of the dynamic viscosity of water with absolute temperature is given as Using these tabulated data, develop a relation for viscosity in the form of μ = μ(T) = A + BT + CT2 + DT3 + ET4. Using the relation develope

> An ideal Otto cycle has a compression ratio of 7. At the beginning of the compression process, P1 = 90 kPa, T1 = 27°C, and V1 = 0.004 m3. The maximum cycle temperature is 1127°C. For each repetition of the cycle, calculate the heat rejection and the net-

> What is the no-slip condition? What causes it?

> A spark-ignition engine has a compression ratio of 10, an isentropic compression efficiency of 85 percent, and an isentropic expansion efficiency of 95 percent. At the beginning of the compression, the air in the cylinder is at 13 psia and 60°F. The maxi

> The analysis of a propeller that operates in water at 60°F shows that the pressure at the tips of the propeller drops to 0.1 psia at high speeds. Determine if there is a danger of cavitation for this propeller.

> Repeat Prob. 9–32 using constant specific heats at room temperature. Data from Prob. 9-32: An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 95 kPa and 27°C, and 750 kJ/kg of heat is transferred to

> A can of soft drink at room temperature is put into the refrigerator so that it will cool. Would you model the can of soft drink as a closed system or as an open system? Explain.

> The diameter of one arm of a U-tube is 5 mm while the other arm is large. If the U-tube contains some water, and both surfaces are exposed to atmospheric pressure, determine the difference between the water levels in the two arms.

> Reconsider Prob. 9–32. Using appropriate software, study the effect of varying the compression ratio from 5 to 10. Plot the net work output and thermal efficiency as a function of the compression ratio. Plot the T-s and P-v diagrams for the cycle when th

> Consider a 55-cm-long journal bearing that is lubricated with oil whose viscosity is 0.1 kg/m⋅s at 20°C at the beginning of operation and 0.008 kg/m⋅s at the anticipated steady operating temperature of 80°C. The diameter of the shaft is 8 cm, and the ave

> An ideal Otto cycle has a compression ratio of 8. At the beginning of the compression process, air is at 95 kPa and 27°C, and 750 kJ/kg of heat is transferred to air during the constant volume heat addition process. Taking into account the variation of s

> Nutrients dissolved in water are carried to upper parts of plants by tiny tubes partly because of the capillary effect. Determine how high the water solution will rise in a tree in a 0.0026-mm diameter tube as a result of the capillary effect. Treat the

> Reconsider Prob. 9–30E. Determine the rate of heat addition and rejection for this ideal Otto cycle when it produces 140 hp. Data from Prob. 9-30: Determine the mean effective pressure of an ideal Otto cycle that uses air as the working fluid; its state

> Contrary to what you might expect, a solid steel ball can float on water due to the surface tension effect. Determine the maximum diameter of a steel ball that would float on water at 10°C. What would your answer be for an aluminum ball? Take the densiti

> Determine the mean effective pressure of an ideal Otto cycle that uses air as the working fluid; its state at the beginning of the compression is 14 psia and 60°F; its temperature at the end of the combustion is 1500°F; and its compression ratio is 9. Us

> A capillary tube is immersed vertically in a water container. Knowing that water starts to evaporate when the pressure drops below 2 kPa, determine the maximum capillary rise and tube diameter for this maximum-rise case. Take the contact angle at the inn

> Why is the Carnot cycle not suitable as an ideal cycle for all power-producing cyclic devices?

> A manometer measures a pressure difference as 40 inches of water. What is this pressure difference in pound force per square inch, psi?

> A 0.018-in-diameter glass tube is inserted into mercury, which makes a contact angle of 140° with glass. Determine the capillary drop of mercury in the tube at 68°F.

> What is the difference between fuel-injected gasoline engines and diesel engines?